1981 - 2018 Centre for Environment, Fisheries & Aquaculture Science (Cefas) Eel survey records from estuaries around England and associated physical and environmental factors 1981-2018
Data explored included long-term catches of eels in transitional and costal waters of England from 1981 to 2018 from the <span style="display: inline !important; float: none; background-color: #ffffff; color: #555555; font-family: 'Open Sans',sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;">...</span> <span style="display: inline !important; float: none; background-color: #ffffff; color: #555555; font-family: 'Open Sans',sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;">...</span>
dataset
http://data.cefas.co.uk/#/View/20473/
function: order
CEFAS9f16c10a-feee-4a5b-801e-5d8a6d2ccfed
http://www.cefas.co.uk/
eng
OGP
urn:ogc:def:crs:EPSG::4326
<span style="background-color: #ffffff;">...</span> <span style="background-color: #ffffff;">...</span> <span style="background-color: #ffffff;">...</span> <span style="background-color: #ffffff;">...</span> <span style="background-color: #ffffff;">...</span> <span style="background-color: #ffffff;">...</span> <span style="background-color: #ffffff;">...</span>
biota
revision
2011-03-25
publication
2008-06-01
publication
2008-06-01
-6
2
54.5
50
revision
2010-05-18
1981-01-01T00:00:00.000Z
2018-12-31T00:00:00.000Z
publication
2020-11-12
notPlanned
<span style="display: inline !important; float: none; background-color: #ffffff; color: #555555; font-family: 'Open Sans',sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;">...</span> <span style="display: inline !important; float: none; background-color: #ffffff; color: #555555; font-family: 'Open Sans',sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;">...</span> <span style="display: inline !important; float: none; background-color: #ffffff; color: #555555; font-family: 'Open Sans',sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;">...</span> The eel data in transitional waters were sourced from the National Fish Populations Database (NFPD), which compiles fisheries monitoring surveys performed in England by the EA and third parties. Only data from England transitional waters have been collated and explored to date, however a request was submitted to Natural Resources Wales (NRW) for fish data and adjacent environmental measures from Welsh transitional waters, especially those shared with England (e.g. Severn) and should these become available, they will be integrated into the existing dataset during future analyses. In addition, a request was logged with the EA to obtain the most relevant environmental factors (i.e. water temperature and salinity) measured during WFD fish surveys. Some physical characteristics of each RBD, estuary and survey site were added to the eel survey data. The latitude of the survey site was added as well as the latitude of the centre of the estuary and RBD. The WFD TraC shapefile was used to separate between transitional and coastal data, as investigating coastal eel distribution and abundance was not in the scope of this study (being subjects of future project phases). This shapefile was also used to calculate the extent of each RBD and estuary and to determine which coast each site is exposed to. The WFD river basin shapefile was used in conjunction with the barriers shapefile from the Environment Agency’s Barrier Database to calculate the number of obstructions to eel movement present within each RBD. The ratio between fresh and transitional waters per RBD was calculated using habitat specific wetted areas for the UK from the ICES 2019 WGEEL report. Seabed habitat and substrate data were collected from the EMODnet Seabed Habitats and the bathymetry map was provided by the British Oceanographic Data Centre. Other geographical information such as Euclidean distance to the nearest coast and distance from the Sargasso Sea were also calculated for each survey site. For determining the distance from each survey site to the coast, a shapefile from ESRI countries shapefile was used to define the coastline. The distance to the Sargasso sea was measured to a point in the centre of the Sargasso Sea, the exact extent of which is not clear, but for the purpose of this study a point located at 34°18'25.7"N, 66°16'10.3"W. The classification of drying extent was derived from calculating the percentage of each estuary that is exposed at mean low tide. This was done by using the intertidal shapefile provided by the Environment Agency upon request and the WFD transitional water bodies shapefile (Environment Agency, 2020a) to determine the extent of the intertidal zone. As none of the estuaries in the survey sites become completely desiccated, drying extent was classified into four categories depending on the percentage of the estuary that became exposed (<25, 25–50, 50–75 and >75). Sites and estuaries were classified as either sheltered, semi-exposed or exposed based on the level of exposure to the open sea. Level of exposure was calculated in ArcGis Pro 2.5.0, using a 1.5 km diameter circle and moving it towards the inlet of an estuary until contact was made with the coast at two points. A line was drawn between these two points and waters inside this line were classified as sheltered. A larger, 15 km diameter, circle was used to classify semi-exposed and exposed transitional waters, and this circle was moved towards the coast until the contact was made at two points and a second line was drawn between those two points. Water between the two lines was classified as semi-exposed and the water outside the second line was defined as exposed. The width of the mouth of each estuary was also measured as an indication of accessibility for the European eel and was also used to indicate exposure at estuarine level. Transitional water characterisation already exists for the UK under the WFD and is based on mixing, salinity, tidal range, exposure, depth and substratum type. As this is also a basis for designing fish surveys across different estuaries, WFD classification of transitional water bodies was requested from the Environment Agency and this was added to each survey site as a transitional waterbody type for use in future analyses.
Public data (Crown Copyright) - Open Government Licence Terms and Conditions apply
Public data (Crown Copyright) - Open Government Licence Terms and Conditions apply
Data Manager
Centre for Environment, Fisheries & Aquaculture Science
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
+44 (0)1502 562244
originator
Data Manager
Centre for Environment, Fisheries & Aquaculture Science
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
+44 (0)1502 562244
custodian
Data Manager
Centre for Environment, Fisheries & Aquaculture Science
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
+44 (0)1502 562244
pointOfContact
2020-11-12T14:31:18